Thermoelectric cooling and heating comprises use of p-type and n-type thermoelectric, semiconductor materials interspersed with each other, and formed into couples by electrically conductive interconnects.
In conventional devices, the interconnects extend from the top of a first element to the top of a second, adjacent element, from the bottom of the second element to the bottom of a third, adjacent element, from the top of the third element to the top of a fourth, adjacent element, and so forth. Each element and each interconnect are both insulated from adjacent elements and interconnects, respectively by space, or by material which is both electrically and thermally insulative. The top and bottom interconnects are typically soldered to respective electrically insulative, thermally conductive top headers and bottom headers.
In “stacked” devices on the other hand, the p-type devices are separated from interspersed n-type devices by electrically and thermally conductive interconnects; the even numbered interconnects extend outwardly in a first direction, and the odd numbered interconnects extend outwardly in a second direction opposite to the first direction. The p-type and n-type elements contacting each interconnect form a thermoelectric couple therewith.
Both the conventional devices and the stacked devices are illustrated in U.S. Pat. No. 5,254,178, both using bulk elements; FIG. 18 illustrates conventional devices and FIG. 1 illustrates stacked devices.
Thermoelectric device performance depends on the well-known thermoelectric figure of merit, ZT, of thermoelectric elements, which may be expressed ZT=(α2T/ρKt) where
α=Seebeck coefficient
T=temperature (K)
ρ=electrical resistivity
Kt=thermal conductivity
Traditionally, the thermoelectric elements (sometimes “T. E.” hereinafter) configured in a conventional device consisted of homogeneous (or bulk) semiconductor alloys of the p-type and of the n-type. Bulk elements with a ZT of about 1.0 provided an overall device ZT of about 0.7-0.9. Then, thin-film superlattice thermoelectric elements were shown to have, at the element level, higher figures of merit, which translate into a higher coefficient of performance (COP), than do the homogenous (bulk) elements at the element level. However, it has been shown that the thin-film superlattice elements, having an average element ZT of about 2, when configured in a conventional device, provide an overall figure of merit of about 0.5, and therefore do not improve overall device COP.